1. Field of Invention
This invention relates to methods for burning liquid fuels in oil burners of furnaces and the like and particularly to a method for reducing the production of NO.sub.x gases while producing a stable flame during combustion in an oil burner.
2. Description of the Prior Art
An oil fuel burner comprises an oil sprayer or atomizer, an air supply and a stabilizer. The sprayer may be a pressure jet system utilizing pressure energy in the oil supply or it may utilize a second fluid (steam or air) to create a fine dispersion of the oil or to assist the pressure jet action. The air supply is essential for combustion. To ensure rapid mixing of the fuel and air, this air supply is normally in a highly turbulent condition. The stabilizer serves to provide, within the turbulent air supply, a quiescent or circulating flow zone in which a flame may be initiated and maintained. The stabilizer is usually a bluff body positioned within the air flow region and shaped to give the required quiescent zone.
A bluff body stabilizer in the combustion zone of a boiler is subject to damage by radiation and corrosion. This damage occurs particularly to a stabilizer of a burner which is out of service but which is in a hot furnace where other burners are operating. A further disadvantage of the bluff body type of stabilizer is that it necessarily obstructs the main air flow.
NO.sub.x gases have been identified as a major source of air pollution in the United States. Oil burners designed to inhibit the production of NO.sub.x gases are known wherein a jet of oil is introduced into a flame through a center passage and flue gas mixed with air is introduced through surrounding passages. U.S. Pat. No. 3,743,471 is an example of one such oil burner requiring a relatively substantial quantity of flue gas for this purpose. Methods and apparatus for controlling the production of NO.sub.x gases using flue gas in a fuel oil staged combustion process are disclosed in U.S. Pat. No. 3,868,211. U.S. Pat. No. 3,880,570 discloses a method of atomizing fuel oil and of utilizing recirculated flue gas to inhibit the production of NO.sub.x gases.